Solid phosphoric acid catalyst

ABSTRACT

A novel solid phosphoric acid catalyst composition is disclosed. The composite comprises solid phosphoric acid and a refractory oxide binder. The composite is characterized in that 25.0 volume percent or less of the total catalyst pore volume consists of pores having a diameter of 10,000  ANGSTROM  or greater. An improvement in catalyst activity and stability is observed when such a catalyst is utilized in a hydrocarbon conversion process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of prior copending application Ser. No.290,477 filed Dec. 29, 1988, now U.S. Pat. No. 4,912,279.

BACKGROUND OF THE INVENTION

This invention relates to a solid phosphoric acid catalyst compositethat is characterized in that 25.0 percent or less of the total catalystpore volume consists of pores having a diameter of 10,000 Å or greater.

Solid phosphoric acid is the name which has come into use for a calcinedmixture of an acid of phosphorus and a porous binder material such askieselguhr, infusorial earth, and diatomaceous earth. Solid phosphoricacid catalysts for years have been virtually the only catalystseffective in the polymerization of normally gaseous olefins to formnormally liquid hydrocarbons. Mixtures of propane and propylene, butaneand butylene, and ethane and ethylene are the chief feedstocks to thepolymerization process. Additionally, solid phosphoric acid catalystsare very useful in catalyzing the alkylation of aromatic hydrocarbonswith aliphatic hydrocarbons. Especially for alkylating benzene withpropylene to produce cumene.

DESCRIPTION OF THE PRIOR ART

Solid phosphoric acid catalysts that have certain properties, additives,formulations, and the like are well known in the art to provide astronger, more active, and longer lasting catalyst. However, a solidphosphoric acid catalyst composite characterized in that 25.0 percent orless of the total catalyst composite pore volume consists of poreshaving a diameter of 10,000 Å or larger and exhibiting improvedstability in a catalytic condensation reaction has heretofore beenunknown.

Basic recipes for solid phosphoric acid catalyst composites are wellknown and disclosed for example in U.S. Pat. No. 2,586,852 whichdescribes a solid phosphoric acid comprising a mixture of kaolin, acrystalline silica, and phosphoric acid.

Porous binder materials have been known to improve the performancecharacteristics of a solid phosphoric acid catalyst composite. U.S. Pat.No. 3,044,964 describes a solid phosphoric acid catalyst compositecomprising phosphoric acid and a natural porous silica material. Inaddition, this catalyst could comprise binders that were not naturallyporous.

The optimization of a solid phosphoric acid catalyst on the basis ofpore volume is relatively unknown in the art. U.S. Pat. No. 3,661,801was the sole reference discovered which discloses a solid phosphoricacid catalyst composite manufactured to obtain a specific pore volumedistribution. The catalyst disclosed has from 0.2 to 0.4 cc/g of poresgreater than 350 Å in diameter and from 0.07 to 0.20 cc/g of poresgreater than 9,000 Å in diameter. Therefore, at minimum, the percentageof catalyst pore volume of this prior art catalyst that is comprised ofpores greater than 9,000 Å is 17.5 percent or more or 0.07 cc/g inabsolute amounts. Additionally, such a catalyst has been disclosed asbeing manufactured by a method which results only in a sphericallyshaped catalyst. All of these factors distinguish the catalyst preparedby the method disclosed in the '801 patent from the catalyst of thisinvention.

U.S. Pat. No. 3,520,945 teaches the art of maintaining proper control ofwater injection into the reaction zone of alkylation and oligomerizationprocesses, including those processes that utilize solid phosphoriccatalyst.

U.S. Pat. No. 3,527,823 teaches the practice of operating a two-phasealkylation reaction zone with net flow upwards through the reactor andin the presence of an unreactive vapor dispersant.

U.S. Pat. No. 3,551,510 teaches that an alkyl aromatic compound may beproduced by the steps of alkylation, transalkylation, and separation.

OBJECTS AND EMBODIMENTS

A principal objective of this invention is to provide an improved solidphosphoric acid catalyst. The improved catalyst exhibits enhancedstability in comparison to similar catalysts of the prior art. Thisimprovement in activity and stability is due to the unique pore volumedistribution of the instant catalyst.

Accordingly, a broad embodiment of the present invention is a solidphosphoric acid catalyst composite. The solid phosphoric acid catalystcomposite comprises solid phosphoric acid and a binder material. Thecatalyst is characterized in that 25.0 percent or less of the totalcatalyst composite pore volume consists of pores having a diameter of10,000 Å or larger. The solid phosphoric acid catalyst composite isfurther characterized in that the binder material is preferably aninorganic oxide material and most preferably a siliceous material suchas diatomaceous earth, kieselguhr, or artificially prepared silicas ormixtures thereof.

In a preferred embodiment, the solid phosphoric acid catalystcomposition is in the form of an extrudate and comprises phosphoric acidand an inorganic oxide binder. The preferred catalyst is characterizedin that 17.5 percent or less of the catalyst composite extrudate porevolume consists of pores having diameters of 10,000 Å or larger. Thecatalyst is further characterized in that the total catalyst compositeextrudate pore volume is about 0.28 cc/g or less with the absolute porevolume for the pores having diameters of 10,000 Å or larger being 0.07cc/g or less. Finally, it is preferred that the instant catalystcomposite comprise at least 60 wt. % P₂ O₅.

DETAILED DESCRIPTION OF THE INVENTION

Solid phosphoric acid catalysts are well known for their utility invarious important hydrocarbon conversion processes. However, there havealways been problems associated with the use of a solid phosphoric acidcatalyst in such processes including catalyst dissolution, poor catalystphysical strength, poor catalyst stability, and the like. Therefore,strong catalysts exhibiting high activity and stability are always beingpursued. To approach this goal of manufacturing a strong, high activity,long-life catalyst, we have found that pore volume is a critical factorin the stability of a solid phosphoric acid with the reduction inmacropore volume, i.e. pores greater than 10,000 Å in diameter, being ofgreat importance.

It is a critical aspect of this invention that the catalyst comprise25.0 percent or less of its pore volume in pores greater than 10,000 Åin diameter. It is most preferred that pores of 10,000 Å or greater makeup only 17.5 percent or less of the total catalyst pore volume. It isbelieved that the large amount of macropore volume not only weakens thestrength of the extrudates but also increases the carbon buildup duringusage caused by the enhanced pore diffusion by macroporosity. Highercarbon buildup during the reaction could potentially lead to fastercatalyst deactivation and catalyst swelling to cause higher than normalreactor pressure drop.

In addition, it has been observed that total pore volume of the catalystis also related to catalyst stability. Therefore, it is preferred thatthe total catalyst pore volume is at most 0.28 cc/g and preferably atmost 0.23 cc/g.

The essential and active ingredient of the solid phosphoric acidcatalyst herein contemplated is an acid of phosphorus, preferably one inwhich the phosphorus has a valence of +5. The acid may constitute fromabout 60 to about 80 wt. % or more of the catalyst mixture ultimatelyproduced. Of the various acids of phosphorus, orthophosphoric acid (H₃PO₄) and pyrophosphoric acid (H₄ P₂ O₇) find general application in theprimary mixtures, due mainly to their cheapness and to the readinesswith which they may be procured, although the catalyst compositeproduced is not restricted to their use but may employ any of the otheracids of phosphorus insofar as they are adaptable. It is not intended toinfer, however, that the different acids of phosphorus, which may beemployed will produced catalyst which have identical affects upon anygiven organic reactions as each of the catalysts produced from differentacids and by slightly varied procedure will exert its own characteristicaction. However, it is believed that the catalyst produced as disclosedherein will have superior hydrocarbon conversion properties incomparison to catalysts without the pore volume distribution disclosedherein.

In using orthophosphoric acid as a primary ingredient, differentconcentrations of the aqueous solution may be employed fromapproximately 75 percent to 100 percent. An acid containing some freephosphorus pentoxide may even be used. By this is meant that the orthoacid may contain a definite percentage of the pyro acid corresponding tothe primary phase of dehydration of the orthophosphoric acid. Withinthese concentration ranges, the acids will be liquids of varyingviscosities, and will readily mix with adsorbent materials. In practice,it has been found that pyrophosphoric acid corresponding to the formulaH₄ P₂ O₇ can be incorporated with binder materials at temperaturessomewhat above its melting point (61° C.) and that the period of heatingwhich is given to the pyro acid adsorbent mixtures may be different fromthat used when the ortho acid is so employed.

Triphosphoric acid which may be represented by the formula H₅ P₃ O₁₀ mayalso be used as a starting material for preparation of the catalyst ofthis invention. These catalytic compositions may also be prepared fromthe siliceous materials mentioned herein and phosphoric acid mixturescontaining orthophosphoric, pyrophosphoric, triphosphoric, and otherpolyphosphoric acids.

The binder material which may be employed as a component of the solidphosphoric acid catalyst composite may be any material that is able toadsorb or bind with the phosphoric acid component of the catalystcomposite. One such group of material is refractory inorganic oxidessuch as alumina, silica, or other metal oxides such as oxides ofmagnesium, calcium, phosphorus, and titanium, or mixtures thereof toname but a few.

It is preferred that the binder material be a siliceous material.Examples of such siliceous or SiO₂ -containing materials which areuseful as the binder component of the instant solid phosphoric acidcatalyst include kieselguhr, diatomaceous earth, infusorial earth,kaolin, fullers earth, or artificially prepared porous silica ormixtures thereof. It is most preferred that the siliceous bindermaterial is kieselguhr. However, it is noted that the terms infusorialearth, kieselguhr, and diatomaceous earth and in general such naturallyoccurring porous siliceous materials will be used and referred tointerchangeably and on an equivalent basis in general in connection withthe present invention.

One method that may be used to produce a solid phosphoric acid catalystcomposite having the desired pore volume characteristics of the catalystof this invention is to closely control the particle size of the bindermaterial. Most binder materials typically contain particles varyinggreatly in size. It is anticipated that by using very small sizedparticles of binder material, the resulting solid phosphoric acidcatalyst composite will be more compact and will thus contain fewerpores greater than 10,000 Å in diameter, in comparison to a catalystthat was manufactured with larger binder particles.

Small binder particles can be obtained in a variety of manners. Thebinder material can be classified with screens to capture only thesmallest particles. Alternatively, the binder materials can bemechanically sized using an Eiger mill, or a ball mill, or the like tobreak the larger particles into smaller particles useful in the instantsolid phosphoric acid catalyst composite. If binder classification isused to produce the catalyst of the instant invention, then it ispreferred that the binder material particle size ranges from 1 to about150 microns.

In producing the catalyst composites which are utilized in the presentinvention, an oxygen acid of phosphorus and the solid binder materialdescribed above are mixed at a temperature of from about 10° to about232° C. and preferably at a temperature of from about 95° to about 180°C. to form a composite. Thus, satisfactory results have been obtained byheating polyphosphoric acid (82% P₂ O₅ content) at a temperature ofabout 170° C. and then mixing this hot acid with diatomaceous earthwhich has previously been at room temperature. The polyphosphoric acidand diatomaceous earth form a composite in which the weight ratio ofphosphorus pentoxide to diatomaceous adsorbent is from about 1.5 toabout 7.5. This composite is slightly moist to almost dry in appearancebut becomes plastic when subjected to pressure in a hydraulic press-typeor auger-type extruder by which the composite is formed into pieces thatare cut into shaped particles.

The extrusion of the phosphoric acid/binder mixture is another step inthe catalyst manufacturing process in which the porosity of the catalystcomposite can be optimized to reduce the amount of pores greater than10,000 Å in the catalyst composite. Extrusion may be used to controlcatalyst porosity in a number of ways essentially by controllingextrusion back-pressure. Generally, the greater the extrusion pressure,the more compact or the lower the porosity, pore volume, and porediameter of the catalyst. Extrusion back-pressure can be varied by avariety of methods. One method is to vary the cross-sectional area ofholes in the extruder die plate. Another method is to vary the moisturecontent of the dough being extruded with a drier dough creating moreback-pressure. A further method is related to the intensity or energyexerted in extruding the instant catalyst composite. An extrudate may beproduced in an extrusion apparatus that comprises a screw that rotates,or that comprises a ram. Both types of apparatuses compact the doughbefore extrusion through the die plate. By varying screw speed orramming intensity along with other extrusion variables, such asscrew-to-barrel clearances, screw pitch, and the like, more extrusionenergy can be expended in compacting and extruding the catalystprecursor dough.

What is important about the extrusion variables and other variablesaffecting the catalyst is that: (1) the desired catalyst porositydistribution is known; and (2) extrusion and other process variablesaffecting the finished catalyst are understood and can be controlled.Those familiar with extrusion will certainly understand the contributionof the variables listed above in controlling the extended catalystporosity and will therefore be able to control such variables toconsistently produce a solid phosphoric acid catalyst of this invention.

It is finally preferred that the solid phosphoric acid catalyst of thisinvention is manufactured in the form of an extrudate. It is believedthat the instant catalyst can be manufactured in many shapes with therequisite pore diameter/pore volume distribution. However, it is feltthat such important properties will be easier to control if the catalystcomposite is in extrudate form. Also, extrusion is typically anefficient and cheap method of producing a formed catalyst particle.

The catalyst composite formed, for example by extrusion, is amorphous(or green) and must undergo a crystallization step that places thecatalyst composite in a crystalline form ready for use in a hydrocarbonconversion process. Typically, the crystallization step is calcination.The calcination of the amorphous extrudate may be accomplished in anyknown calcination process of the prior art which controls temperatureand time, and optionally, moisture level in the calcination zone. Thus,the crystallization of the catalyst may occur in a calcination apparatuscontaining a single calcination zone, two calcination zones, or three ormore calcination zones. A calcination zone is characterized in that atleast the temperature of the zone can be controlled independently of theother calcination zones.

The calcination variables noted above are believed to directly impact onthe final type and amount of ores and pore volume in the calcined solidphosphoric acid catalysts. As mentioned, it is preferred that thefinished solid phosphoric acid catalyst be characterized in that 25.0percent or less of the total catalyst pore volume consists of poreshaving a diameter of 10,000 or larger. Further, it is preferred that thecatalyst have a total pore volume of 0.28 cc/g or less.

Temperature is a first critical calcination condition. Temperature isimportant in both dehydrating the amorphous material and in controllingthe type of crystallites produced as a result of the calcination. It iswell known that high calcination temperatures, especially those above500° C. result in a solid phosphoric acid catalyst comprisingessentially only crystallites of silicon pyrophosphate. As a result ofdesiring a catalyst with crystallites of both silicon orthophosphate andsilicon pyrophosphate, it was determined that calcination temperaturesranging from 100° to 450° C. were most desirable and especiallycalcination temperatures between 350° and 450° C.

In conjunction with controlling calcination temperature, it is knownthat the steam, or moisture, content of the calcination zone can becontrolled closely to produce a finished solid phosphoric acid catalystcomposite exhibiting the desired porosity and pore volume. It is desiredthat the steam content of the vapor of the calcination zone or zones begreater than 5.0 mole percent based upon the total vapor rate to thecalciner to impart the desired porosity characteristics into the instantcatalyst.

It should be noted that controlling the steam content of the calcinervapors does not necessarily mean that all or even part of the steam tothe calciner must be added from an outside source. It is quite possiblethat much of the steam will be present in the vapor in the calcinationzone as a result of evaporation of water from the catalyst during thecalcination. Steam addition to the calcination zone or zones will likelybe required but the variable might also be controlled by controllingsuch variables as total vapor rate through the calcination zone orzones, temperature, and green catalyst moisture content among others.

Time in the calciner is also an important variable. Typically, the totalcalcination time will vary from 20 to 120 minutes. When more than onecalcination zone is used, the total time in each may vary such that thetotal calcination time ranges from 20 to 120 minutes.

It is a further preferred aspect of this invention that where there ismore than one calcination zone, at least one calcination zone must beoperated at the conditions above. It is further preferred that theterminal (or final) calcination zone in a multiple calcination zonecalciner is operated at the desired process conditions detailed above.This is not to say that other calcination zones besides the terminalzone cannot be operated at the preferred operating conditions, but it isbelieved that operating the final calcination zone at the highesttemperature is the most efficient way of producing the catalystdisclosed herein.

In addition, it is preferred that the moisture level in the terminalcalcination zone be 5.0 mole percent or greater. A solid phosphoric acidcatalyst calcined by the method above will generally have the desiredporosity as described hereinabove. As a result, 25.0 percent or less ofits total pore volume of the instant catalyst composite will comprisepores of 10,000 Å or greater as analyzed by the mercury intrusionmethod.

The catalyst surface area and pore volume distribution are typicallydetermined by mercury intrusion and extrusion methods. The mercuryintrusion and extrusion methods are widely used in the catalysis sciencefor catalyst porosity characterization. Detail discussion can be foundin literature references such as A Review of Mercury Porosimetry by H.M. Rootare in Advanced Experimental Techniques in Powder Metallurgy, pp225-252, Plenum Press, 1970, A Generalized Analysis for MercuryPorosimetry by R. W. Smithmick in Powder Technology, 33 (1982) pp201-209, and Advances in Experimental Techniques for Mercury IntrusionPorosimetry by D. N. Winslow in Surface Colloid Science, vol. 13.

The catalyst of this invention is useful in catalytic condensation,aromatic alkylation, and other types of hydrocarbon conversion processeswhere solid phosphoric acid catalysts have been known to be useful. Whenemployed in the conversion of olefinic hydrocarbons into polymers, thecatalyst formed as heretofore set forth, is preferably employed as agranular layer in a heated reactor which is generally made from steel,and through which the preheated hydrocarbon fraction is directed. Thus,the solid catalyst of this process may be employed for treating mixturesof olefin-containing hydrocarbon vapors to effect olefin polymerization,but the same catalyst may also be used at operating conditions suitablefor maintaining liquid phase operation during polymerization of olefinichydrocarbons, such as butylenes, to produce gasoline fractions.

When used for polymerizing normally gaseous olefins, the particles ofthe catalyst are generally placed in vertical cylindrical treatingtowers or in fixed beds in reactors or towers and the gases containingolefins are passed downwardly through the reactors or towers attemperatures of 170° to 290° C. and pressures of 6 to 102 atmospheres.These conditions are particularly applicable when dealing witholefin-containing material which may contain from approximately 10 to 50percent or more or propylene and butylenes. When operating on a mixturecomprising essentially propylene and butylenes, this catalyst iseffective at temperatures from about 140° to about 250° C. and at apressure of from about 34 to about 102 atmospheres.

The catalyst of this invention is also useful in the alkylation ofaromatic hydrocarbons with an alkylating agent. The alkylating agentwhich may be charged to the alkylation reaction zone may be selectedfrom a group of diverse materials including monoolefins, diolefins,polyolefins, acetylenic hydrocarbons, and also alkylhalides, alcohols,ethers, esters, the latter including the alkylsulfates, alkylphosphates,and various esters of carboxylic acids. The preferred olefin-actingcompounds are olefinic hydrocarbons which comprise monoolefinscontaining one double bond per molecule. Monoolefins which may beutilized as olefin-acting compounds in the process of the presentinvention are either normally gaseous or normally liquid and includeethylene, propylene, 1-butene, 2-butene, isobutylene, and the highermolecular weight normally liquid olefins such as the various pentenes,hexenes, heptenes, octenes, and mixtures thereof, and still highermolecular weight liquid olefins, the latter including various olefinpolymers having from about 9 to about 18 carbon atoms per moleculeincluding propylene trimer, propylene tetramer, propylene pentamer, etc.Cycloolefins such as cyclopentene, methylcyclopentene, cyclohexene,methylcyclohexene, etc., may also be utilized, although not necessarilywith equivalent results. Other hydrocarbons such as paraffins,naphthenes, and the like containing 2 to 18 carbon atoms may also bepresent in the alkylating agent. When the catalyst of the presentinvention is used for catalyzing an aromatic alkylation reaction, it ispreferred that the monoolefin contains at least 2 and not more than 14carbon atoms. More specifically, it is preferred that the monoolefin ispropylene.

The aromatic substrate which is charged to the alkylation reaction zonein admixture with the alkylating agent may be selected from a group ofaromatic compounds which include individually and in admixture, benzeneand monocyclic alkyl-substituted benzene of from 7 to 12 carbon atomshaving the structure: ##STR1## where R is methyl, ethyl, or acombination thereof, and n is an integer from 1 to 5. In other words,the aromatic substrate portion of the feedstock may be benzene, analkylaromatic containing from 1 to 5 methyl and/or ethyl groupsubstituents, and mixtures thereof. Non-limiting examples of suchfeedstock compounds include benzene, toluene, xylene, ethylbenzene,mesitylene (1,3,5-trimethylbenzene) and mixtures thereof. It isspecifically preferred that the aromatic substrate is benzene.

In a continuous process for alkylating aromatic hydrocarbons witholefins, the previously described reactants are continuously fed into apressure vessel containing solid phosphoric acid catalyst of thisinvention. The feed admixture may be introduced into the alkylationreaction zone containing the alkylation catalyst at a constant rate, oralternatively, at a variable rate. Normally, the aromatic substrate andolefinic alkylating agent are contacted at a molar ratio of from about1:1 to 20:1 and preferably from about 2:1 to 8:1. The preferred molarfeed ratios help to maximize the catalyst life cycle by minimizing thedeactivation of the catalyst by coke and heavy material deposition uponthe catalyst. The catalyst may be contained in one bed within a reactorvessel or divided up among a plurality of beds within a reactor. Thealkylation reaction system may contain one or more reaction vessels inseries. The feed to the reaction zone can flow vertically upwards, ordownwards through the catalyst bed in a typical plug flow reactor, orhorizontally across the catalyst bed in a radial flow type reactor.

In some cases, in order to maintain the reaction temperature in thepreferred range and thus reduce the formation of unwantedpolyalkylaromatics, it may be desirable to quench the reactants todissipate heat of reaction. A quench stream comprised of the alkylatingagent olefin, the alkylating agent or a portion of the reactor effluentstream, or mixtures thereof may be injected into the alkylation reactorsystem in order to dissipate heat and supply additional amounts ofolefin alkylating agent and unreacted aromatic substrate at variouslocations within the reaction zone. This is accomplished for example ina single-stage reactor by multiple injection of the aforementionedquench stream components into the reaction zone via strategically placedinlet lines leading into said reaction zone. The amount and compositionof quench material injected into either a single stage reaction systemor multi-stage reaction system may be varied according to need. Benefitsresulting from multiple quench injection include elimination of costlycooling apparatus in the process, improved selectivity to formation ofthe desired alkylaromatic compound, provision for a larger heat sink andoptimization of the olefin to aromatic compound molar ratio throughoutthe reaction zone, thus resulting in increased yield of the desiredmonoalkylated aromatic compound.

Temperatures which are suitable for use in the process herein are thosetemperatures which initiate a reaction between an aromatic substrate andthe particular olefin used to selectively produce the desiredmonoalkylaromatic compound. Generally, temperatures suitable for use arefrom about 100° to about 390° C., especially from about 150° to about275° C. Pressures which are suitable for use herein preferably are aboveabout 1 atmosphere but should not be in excess of about 130 atmospheres.An especially desirable pressure range is from about 10 to about 40atmospheres; with a liquid hourly space velocity (LHSV) based upon thebenzene feed rate of from about 0.5 to about 50 hr⁻¹, and especiallyfrom about 1 to about 10 hr⁻¹. It should be noted that the temperatureand pressure combination used herein is to be such that the alkylationreaction takes place in essentially the liquid phase. In a liquid phaseprocess for producing alkylaromatics, the catalyst is continuouslywashed with reactants, thus preventing buildup of coke precursors on thecatalyst. This results in reduced amounts of carbon forming on saidcatalyst in which case, catalyst cycle life is extended as compared to agas phase alkylation process in which coke formation and catalystdeactivation is a major problem.

Additionally, a regulated amount of water is preferably added to thealkylation reaction zone. In order to substantially prevent loss ofwater from the catalyst and subsequent decrease in catalyst activities,an amount of water or water vapor such as steam is added to the chargeso as to substantially balance the water vapor pressure of thealkylation catalyst hereinabove described. This amount of water variesfrom about 0.01 to 6% by volume of the organic material charged to thealkylation reaction zone. The water is then typically removed with thelight by-product stream recovered in the first separation zone.

A substantial portion of the aromatic substrate hydrocarbon andessentially all of the olefin alkylating agent react in the alkylationreaction zone in the presence of the solid phosphoric acid catalyst toform monoalkylaromatic compounds and polyalkylaromatic compounds. Thepreferred product of an alkylation process utilizing the solidphosphoric acid catalyst composite of this invention is cumene.

The following examples are presented to illustrate the catalystcomposite and uses of the catalyst of the present invention and are notintended as an undue limitation on the generally broad scope of theinvention as embodied in the claims.

EXAMPLE I

This example illustrates the general preparation method for theamorphous form phosphoric acid catalyst extrudate that is converted byvarious calcination methods of the subsequent examples into crystallineforms of solid phosphoric acid catalyst with different amounts ofmacropore volume.

Kieselguhr clay and phosphoric acid having a P₂ O₅ content of 82% orgreater were combined at a weight ratio of 1 to 2 at a temperature of170° C. This material was extruded with an extruder through a die toproduce extrudates with approximately 5 mm diameter. Only material withan amorphous character was detected by x-ray analysis of the greenextrudates. The extrudates thus produced were then used in thecalcination experiments described in the following Examples II to V. Thecalcination conditions include temperatures of from 100° C. to 500° C.,moisture levels of from 0 to 25 mole percent based upon the total vaporrate to the calciner, all for a time ranging from 20 to 120 minutes. Thefinal catalysts were analyzed for porosity and pore volume distribution.The pore volume distribution was measured by mercury intrusion with aMicromeritic Autopore 9220.

EXAMPLE II

This example highlights the effect that various calcination conditionshave on the porosity and pore volume distribution of solid phosphorusacid catalysts. A batch of amorphous solid phosphoric acid greenextrudates from Example I was subjected to a calcination process in asmall furnace in batches of 100 to 150 grams. The furnace contained ameans of allowing once through air and steam to be added at a controlrate as well as a means for closely controlling the furnace temperature.After about 50 minutes under only a 3% steam rate in a furnace which hasbeen preheated to 392° C. furnace temperature the catalyst was removedand analyzed for its porosity. The calcined catalyst had a total porevolume of 0.236 cc/g and macropore volume (pore volume greater than10,000 Å) of 0.071 cc/g as measured by mercury intrusion. The macroporevolume therefore represents 30% of the total pore volume. This catalystdoes not fit the definition of the catalyst of this invention.

A second batch of amorphous solid phosphoric acid green extrudates fromExample I was subjected to a calcination process in the same small ovenas in the Example II. After about 50 minutes under 14% steam rate in afurnace which has been preheated to 430° C. temperature followed by 22%steam addition rate for 20 minutes, the catalyst was removed andanalyzed for its porosity. The total pore volume of 0.239 cc/g andmacropore volume (pore volume greater than 10,000 Å of 0.035 cc/g weremeasured by mercury intrusion method. This macropore volume represents15% of the total pore volume. This catalyst falls within theporosity/pore volume distribution of the catalyst of this invention. Itis evident from the example that steam rate to the calcination zone iscritical in producing a catalyst with the porosity and pore volumedistribution of this invention.

EXAMPLE III

A number of solid phosphoric acid catalysts prepared essentially as setforth in Example I were analyzed for total pore volume and pore volumedistribution by mercury intrusion method. This results of this analysiscan be found in Table 1 below.

The analyzed catalysts were then tested for catalyst life by placing thecatalysts in an olefin polymerization process plant with propylene feed.The test was conducted under 68 atmospheres pressure, at a hydrocarbonfeed space velocity of from 1.8 to 2.1, and at a temperature from 150°to 230° C. The testing occurred in a plant operated at constantconversion directed towards making a commercial product. The catalystlife values are all reported relative to catalyst E which had theshortest catalyst life. The end of the catalyst's life was determinedwhen the pressure drop across the catalyst bed became too great tocontinue processing.

                  TABLE 1                                                         ______________________________________                                        Catalyst     A       B       C     D     E                                    ______________________________________                                        Catalyst Life (gal/lb)                                                                     2.43    1.84    1.50  1.48  1.0                                  Total Pore Volume                                                                          0.183   0.215   0.197 0.187 0.212                                (cc/g)                                                                        Pore Volume >10,000                                                                        0.027   0.042   0.045 0.046 0.048                                Å (cc/g)                                                                  % of Volume >10,000                                                                        14.7    19.5    22.8  24.6  22.6                                 Å                                                                         ______________________________________                                    

The data above indicates that there is a definite correlation betweencatalyst life and the percentage of volume of pores above 10,000 Å in asolid phosphoric acid catalyst. The correlation indicated is that thelower the percentage of the catalyst volume contained in pores above10,000 Å in diameter, the greater the catalyst life.

What is claimed is:
 1. A solid phosphoric acid composite comprising oneor more acids of pentacovalent phosphorus in an amount from about 60 toabout 88 weight percent of the composite, adsorbed on a binder which isa refractory inorganic oxide or a siliceous material, said compositehaving a pore volume no more than 0.28 cc/g with 25 percent or less ofthe pore volume arising from pores with a diameter greater than 10,000Å.
 2. The solid phosphoric acid composite of claim 1 where therefractory inorganic oxide is selected from the group consisting ofalumina, magnesium oxide, calcium oxide, titanium oxide, and phosphorusoxides.
 3. The solid phosphoric acid composite of claim 1 where thesiliceous material is selected from the group consisting of silicas,kieselguhr, diatomaceous earth, infusorial earth, kaolin, fullers earth,or combinations thereof.
 4. The solid phosphoric acid composite of claim3 where the siliceous material is diatomaceous earth, kieselguhr, anartificially prepared porous silica, or combinations thereof.
 5. Thesolid phosphoric acid composite of claim 1 where the pore volume of thecomposite is no more than about 0.23 cc/g.
 6. The solid phosphoric acidcomposite of claim 1 where 17.5 percent or less of the pore volumearises from pores with a diameter greater than 10,000 Å.
 7. The solidphosphoric acid composite of claim 1 where the pore volume of thecomposite is no more than about 0.23 cc/g. and 17.5 percent or less ofthe pore volume arises from pores with a diameter greater than 10,000 Å.8. The solid phosphoric acid composite of claim 1 in the form of anextrudate.